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First flu infection muffles effect of related flu viruses

When the next devastating flu pandemic hits — think the swine flu of 2009 or the so-called Asian “bird flu” — how will you fare? That depends partly on the first kind of flu virus you ever contracted and how closely it relates to the flu threat of the moment, researchers now say.

Flu viruses come in groups of strains that share similar proteins. Through statistical modeling of cases of two flu strains over many years, a group of scientists found that the type of protein that humans encounter in their first bout of influenza forms the basis for defending against other flus with the same protein type.

That’s because bodies produce different types of flu-fighting antibodies. For the two flu strains the researchers focused on, this connection meant a 75 percent lower risk of severe illness and about an 80 percent lower risk of death.

Researchers said their findings could lead to new ways of reducing the risks of major flu outbreaks. Because flu strains come in waves and public health workers track which ones might hit a certain country in any given year, these new findings could help predict which age groups are most vulnerable to the dominant strains each year.

If next year’s flu is in one group or family of strains, for example, then people who were exposed to a related strain during an earlier outbreak or during their childhood could have gotten that type of flu first, offering them some protection.

You may still come down with the flu, with all of the associated aches and pains, but in a much milder form. And you might have some protection against any ‘‘novel’’ flu strain that pops up.